ee.Image.reproject

Memaksa gambar dihitung dalam proyeksi dan resolusi tertentu.

Penggunaan	Hasil
Image.reproject(crs, crsTransform, scale)	Gambar

Argumen	Jenis	Detail
ini: image	Gambar	Gambar yang akan diproyeksikan ulang.
crs	Proyeksi	CRS untuk memproyeksikan gambar.
crsTransform	Daftar, default: null	Daftar nilai transformasi CRS. Ini adalah pengurutan baris utama dari matriks transformasi 3x2. Opsi ini tidak dapat digunakan bersama dengan opsi skala, dan menggantikan transformasi apa pun yang sudah ada pada proyeksi.
scale	Float, default: null	Jika skala ditentukan, proyeksi akan diskalakan dengan membagi nilai skala yang ditentukan dengan ukuran nominal meter dalam proyeksi yang ditentukan. Jika skala tidak ditentukan, skala proyeksi yang diberikan akan digunakan.

Contoh

Code Editor (JavaScript)

// Use of ee.Image.reproject is rarely needed and should generally be avoided.
// Defining the projection and scale of analysis should be handled by "scale",
// "crs", and "crsTransform" parameters whenever they are offered by a function.
// It is occasionally useful for forcing computation or visualization at a
// desired scale and projection when alternative methods are not available. In
// this example it is used to compute and visualize terrain slope from a DEM
// composite.

// Calculate mean elevation from two DEM datasets. The resulting composite
// image has a default CRS of WGS84 with 1 degree pixels.
var dem1 = ee.Image('NASA/NASADEM_HGT/001').select('elevation');
var dem2 = ee.Image('CGIAR/SRTM90_V4').select('elevation');
var demMean = ee.ImageCollection([dem1, dem2]).mean();

// Display the DEMs on the map, note that they all render as expected.
var demVisParams = {min: 500, max: 2500};
Map.setCenter(-123.457, 47.815, 11);
Map.addLayer(dem1, demVisParams, 'DEM 1');
Map.addLayer(dem2, demVisParams, 'DEM 2');
Map.addLayer(demMean, demVisParams, 'DEM composite');

// Calculate terrain slope from the composite DEM (WGS84, 1 degree pixel scale).
var demCompSlope = ee.Terrain.slope(demMean);

// Because the composite has 1 degree pixel scale, the slope calculation
// is essenstially meaningless and difficult to even display (you may need to
// zoom out to see the individual 1 degree pixels).
Map.addLayer(demCompSlope, {min: 0, max: 0.3}, 'Slope');

// We can use ee.Image.reproject to force the slope calculation and display
// the result with a reasonable scale of 30 m on WGS84 CRS, for example.
var slopeScale = ee.Terrain.slope(
  demMean.reproject({
    crs: 'EPSG:4326',
    scale: 30
  })
);
Map.addLayer(slopeScale, {min: 0, max: 45}, 'Slope w/ CRS and scale');

// To more precisely control the reprojection, you can use the "crsTransform"
// parameter instead of the "scale" parameter or set the projection according to
// a reference image. For example, here the input composite image for the slope
// function is set to match the grid spacing and alignment of the NASADEM image.
var nasademProj = dem1.projection();
var demMeanReproj = demMean.reproject(nasademProj);
var slopeRefProj = ee.Terrain.slope(demMeanReproj);
Map.addLayer(slopeRefProj, {min: 0, max: 45}, 'Slope w/ reference proj');
print('Reference projection', nasademProj);
print('DEM composite projection', demMeanReproj.projection());

// An alternative method for changing the projection of image composites
// (not accepting the default WGS84 CRS with 1 degree pixel scale) is to
// explicitly set the default projection using ee.Image.setDefaultProjection,
// which will not force resampling, like ee.Image.reproject will.
var demMeanProj = ee.ImageCollection([dem1, dem2]).mean()
                      .setDefaultProjection(nasademProj);
var slopeProj = ee.Terrain.slope(demMeanProj);
Map.addLayer(slopeProj, {min: 0, max: 45}, 'slope w/ default projection set');

Penyiapan Python

Lihat halaman Lingkungan Python untuk mengetahui informasi tentang Python API dan penggunaan geemap untuk pengembangan interaktif.

import ee
import geemap.core as geemap

Colab (Python)

# Use of ee.Image.reproject is rarely needed and should generally be avoided.
# Defining the projection and scale of analysis should be handled by "scale",
# "crs", and "crsTransform" parameters whenever they are offered by a function.
# It is occasionally useful for forcing computation or visualization at a
# desired scale and projection when alternative methods are not available. In
# this example it is used to compute and visualize terrain slope from a DEM
# composite.

# Calculate mean elevation from two DEM datasets. The resulting composite
# image has a default CRS of WGS84 with 1 degree pixels.
dem_1 = ee.Image('NASA/NASADEM_HGT/001').select('elevation')
dem_2 = ee.Image('CGIAR/SRTM90_V4').select('elevation')
dem_mean = ee.ImageCollection([dem_1, dem_2]).mean()

# Display the DEMs on the map, note that they all render as expected.
dem_vis_params = {'min': 500, 'max': 2500}
m = geemap.Map()
m.set_center(-123.457, 47.815, 11)
m.add_layer(dem_1, dem_vis_params, 'DEM 1')
m.add_layer(dem_2, dem_vis_params, 'DEM 2')
m.add_layer(dem_mean, dem_vis_params, 'DEM composite')

# Calculate terrain slope from the composite DEM (WGS84, 1 degree pixel scale).
dem_comp_slope = ee.Terrain.slope(dem_mean)

# Because the composite has 1 degree pixel scale, the slope calculation
# is essenstially meaningless and difficult to even display (you may need to
# zoom out to see the individual 1 degree pixels).
m.add_layer(dem_comp_slope, {'min': 0, 'max': 0.3}, 'Slope')

# We can use ee.Image.reproject to force the slope calculation and display
# the result with a reasonable scale of 30 m on WGS84 CRS, for example.
slope_scale = ee.Terrain.slope(dem_mean.reproject(crs='EPSG:4326', scale=30))
m.add_layer(slope_scale, {'min': 0, 'max': 45}, 'Slope w/ CRS and scale')

# To more precisely control the reprojection, you can use the "crsTransform"
# parameter instead of the "scale" parameter or set the projection according to
# a reference image. For example, here the input composite image for the slope
# function is set to match the grid spacing and alignment of the NASADEM image.
nasadem_proj = dem_1.projection()
dem_mean_reproj = dem_mean.reproject(nasadem_proj)
slope_ref_proj = ee.Terrain.slope(dem_mean_reproj)
m.add_layer(slope_ref_proj, {'min': 0, 'max': 45}, 'Slope w/ reference proj')
display('Reference projection', nasadem_proj)
display('DEM composite projection', dem_mean_reproj.projection())

# An alternative method for changing the projection of image composites
# (not accepting the default WGS84 CRS with 1 degree pixel scale) is to
# explicitly set the default projection using ee.Image.setDefaultProjection,
# which will not force resampling, like ee.Image.reproject will.
dem_mean_proj = (
    ee.ImageCollection([dem_1, dem_2]).mean().setDefaultProjection(nasadem_proj)
)
slope_proj = ee.Terrain.slope(dem_mean_proj)
m.add_layer(
    slope_proj, {'min': 0, 'max': 45}, 'slope w/ default projection set'
)
m